The Senate is preparing to vote again on the DISCLOSE Act for campaign finance reform – and just as with the first vote in July, Democrats are likely heading for failure.

Senate Majority Leader Harry Reid (D-Nev.) announced through a spokesman that he was bringing the DISCLOSE Act back to the floor on Thursday. But it’s all but assured that he’ll not have the 60 votes necessary to overcome a threatened Republican filibuster, with moderate Republicans showing no signs of flinching in their opposition.

New York Sen. Chuck Schumer and other Democratic cosponsors insist there’s more impetus for Republicans to break ranks this time – that special interest money funneling into campaigns now is cause for alarm and that Democrats are willing to accept GOP amendments once the bill is open for floor debate.

“Obviously, there’s tremendous pressure for them not to go the other way, but there are people, I think, on the other side who really believe we ought to have this vote,” Schumer said Wednesday, adding that Democrats are open to pushing back the effective date until the next election cycle, a change Republicans said they had wanted.

But they still don’t seem to be buying in.

Senate Minority Leader Mitch McConnell (R-Ky.) accused Democrats Wednesday of putting their own job security in front of that of Americans, dismissing the move to bring DISCLOSE up for another vote as “pure politics.”

“Today in the Senate, in the middle of the worst recession in memory, the Democratic leadership has decided to spend the next two days on the same failed, partisan campaign spending bill aimed at giving Democrats a political edge,” McConnell said on the floor. “Here we are voting on a bill that amounts to little more than an incumbency protection act for Democrats in Congress.”

All the political motives, however, don’t lie with Democrats. Both parties are seeking to score message victories with the vote.

Republicans, following McConnell’s lead Wednesday, are trying to paint the bill as favoring Democratic interests and the Democrats as out-of-touch for pursuing it. And Democrats are reviving their message for Wall Street reform, claiming Republicans are siding with corporations over everyday Americans.

Some outside advocacy groups, a Democratic aide said, already had plans to meet with key Republicans Thursday to lobby for the bill, which was crafted in response to a controversial Supreme Court decision protecting corporate campaign giving as free speech. And the full day’s lead-up lent itself to more media coverage than the initiative otherwise would have received.

But Senate aides also pointed out that the decision to try to re-open debate on DISCLOSE could be as much about logistics as politics.

When the defense authorization bill failed to clear cloture Tuesday, Democrats needed a measure to fill floor time before the weekend, and the DISCLOSE Act was one of the few measures in their legislative arsenal that was quickly available.

Having failed cloture once, the campaign bill only requires a less strict “motion to recommit” from Reid to call another cloture vote. New legislation likely would need 30 hours after being filed, 30 hours the Senate doesn’t have.

So even if Democrats know they’re likely short of votes Thursday, the alternative was practically nothing.

With the fate of the Bush tax cuts still being haggled over and time running out before this fall’s recess, the only other legislation that has a chance of approval likely would need to be done by unanimous consent because there’s not enough time on the calendar for a days-long, if not weeks-long, formal process on the floor.